The new KEXEC_FILE_LOAD is preferred in the case the platform supports
it because it allows kexec in locked down secure boot mode.

However, some platforms do not support it so fall back to the old
syscall there.

Also provide an option to call the old syscall in case the new syscall
fails with other reason than ENOSYS.

Also document the options.

Signed-off-by: Michal Suchanek <msucha...@suse.de>
---
 kexec/kexec.8 |  9 +++++++++
 kexec/kexec.c | 41 +++++++++++++++--------------------------
 kexec/kexec.h |  2 ++
 3 files changed, 26 insertions(+), 26 deletions(-)

diff --git a/kexec/kexec.8 b/kexec/kexec.8
index e0131b4ea827..7e4df723251d 100644
--- a/kexec/kexec.8
+++ b/kexec/kexec.8
@@ -144,6 +144,15 @@ Load the new kernel for use on panic.
 Specify that the new kernel is of this
 .I type.
 .TP
+.BI \-s\ (\-\-kexec-file-syscall)
+Specify that the new KEXEC_FILE_LOAD syscall should be used exclusively.
+Otherwise KEXEC_FILE_LOAD is tried and when not supported KEXEC_LOAD is used.
+.I type.
+.TP
+.BI \-c\ (\-\-kexec-syscall)
+Specify that the old KEXEC_LOAD syscall should be used exclusively.
+.I type.
+.TP
 .B \-u\ (\-\-unload)
 Unload the current
 .B kexec
diff --git a/kexec/kexec.c b/kexec/kexec.c
index cfd837c1b6bb..25328c02b508 100644
--- a/kexec/kexec.c
+++ b/kexec/kexec.c
@@ -1166,7 +1166,7 @@ static int do_kexec_file_load(int fileind, int argc, char 
**argv,
 
        if (!is_kexec_file_load_implemented()) {
                fprintf(stderr, "syscall kexec_file_load not available.\n");
-               return -1;
+               return -ENOSYS;
        }
 
        if (argc - fileind <= 0) {
@@ -1243,6 +1243,7 @@ int main(int argc, char *argv[])
        int do_unload = 0;
        int do_reuse_initrd = 0;
        int do_kexec_file_syscall = 0;
+       int do_kexec_syscall = 0;
        int do_status = 0;
        void *entry = 0;
        char *type = 0;
@@ -1256,19 +1257,6 @@ int main(int argc, char *argv[])
        };
        static const char short_options[] = KEXEC_ALL_OPT_STR;
 
-       /*
-        * First check if --use-kexec-file-syscall is set. That changes lot of
-        * things
-        */
-       while ((opt = getopt_long(argc, argv, short_options,
-                                 options, 0)) != -1) {
-               switch(opt) {
-               case OPT_KEXEC_FILE_SYSCALL:
-                       do_kexec_file_syscall = 1;
-                       break;
-               }
-       }
-
        /* Reset getopt for the next pass. */
        opterr = 1;
        optind = 1;
@@ -1310,8 +1298,7 @@ int main(int argc, char *argv[])
                        do_shutdown = 0;
                        do_sync = 0;
                        do_unload = 1;
-                       if (do_kexec_file_syscall)
-                               kexec_file_flags |= KEXEC_FILE_UNLOAD;
+                       kexec_file_flags |= KEXEC_FILE_UNLOAD;
                        break;
                case OPT_EXEC:
                        do_load = 0;
@@ -1354,11 +1341,8 @@ int main(int argc, char *argv[])
                        do_exec = 0;
                        do_shutdown = 0;
                        do_sync = 0;
-                       if (do_kexec_file_syscall)
-                               kexec_file_flags |= KEXEC_FILE_ON_CRASH;
-                       else
-                               kexec_flags = KEXEC_ON_CRASH;
-                       break;
+                       kexec_file_flags |= KEXEC_FILE_ON_CRASH;
+                       kexec_flags = KEXEC_ON_CRASH;
                case OPT_MEM_MIN:
                        mem_min = strtoul(optarg, &endptr, 0);
                        if (*endptr) {
@@ -1383,7 +1367,12 @@ int main(int argc, char *argv[])
                        do_reuse_initrd = 1;
                        break;
                case OPT_KEXEC_FILE_SYSCALL:
-                       /* We already parsed it. Nothing to do. */
+                       do_kexec_file_syscall = 1;
+                       do_kexec_syscall = 0;
+                       break;
+               case OPT_KEXEC_SYSCALL:
+                       do_kexec_file_syscall = 0;
+                       do_kexec_syscall = 1;
                        break;
                case OPT_STATUS:
                        do_status = 1;
@@ -1456,16 +1445,16 @@ int main(int argc, char *argv[])
                result = k_status(kexec_flags);
        }
        if (do_unload) {
-               if (do_kexec_file_syscall)
+               if (!do_kexec_syscall)
                        result = kexec_file_unload(kexec_file_flags);
-               else
+               if ((result == -ENOSYS) || !do_kexec_file_syscall)
                        result = k_unload(kexec_flags);
        }
        if (do_load && (result == 0)) {
-               if (do_kexec_file_syscall)
+               if (!do_kexec_syscall)
                        result = do_kexec_file_load(fileind, argc, argv,
                                                 kexec_file_flags);
-               else
+               if ((result == -ENOSYS) || !do_kexec_file_syscall)
                        result = my_load(type, fileind, argc, argv,
                                                kexec_flags, entry);
        }
diff --git a/kexec/kexec.h b/kexec/kexec.h
index 26225d2c002a..7abcec796cae 100644
--- a/kexec/kexec.h
+++ b/kexec/kexec.h
@@ -219,6 +219,7 @@ extern int file_types;
 #define OPT_TYPE               't'
 #define OPT_PANIC              'p'
 #define OPT_KEXEC_FILE_SYSCALL 's'
+#define OPT_KEXEC_SYSCALL      'c'
 #define OPT_STATUS             'S'
 #define OPT_MEM_MIN             256
 #define OPT_MEM_MAX             257
@@ -246,6 +247,7 @@ extern int file_types;
        { "mem-max",            1, 0, OPT_MEM_MAX }, \
        { "reuseinitrd",        0, 0, OPT_REUSE_INITRD }, \
        { "kexec-file-syscall", 0, 0, OPT_KEXEC_FILE_SYSCALL }, \
+       { "kexec-syscall",      0, 0, OPT_KEXEC_SYSCALL }, \
        { "debug",              0, 0, OPT_DEBUG }, \
        { "status",             0, 0, OPT_STATUS }, \
        { "print-ckr-size",     0, 0, OPT_PRINT_CKR_SIZE }, \
-- 
2.13.6


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